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Postfix to infix conversion

This programs gets in a postfix expression and converts it to its infix expression

Submitted By: rameshg87

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Rating:

Views: 9,735

Language: C

Last Modified: June 8, 2007

Snippet

#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
int top=10;
struct tree
{
char ch;
struct tree *next;
struct tree *prev;
}*stack[11];
typedef struct tree tree;
void push(tree *str)
{
if(top<=0)
printf("Stack is Full ");
else
{
stack[top]=str;
top--;
}
}
tree* pop()
{
tree *exp;
if(top>=10)
printf("Stack is Empty ");
else
exp=stack[++top];
return exp;
}
void convert(char exp[])
{
tree *op1,*op2;
tree *temp;
int i;
for(i=0;exp[i]!='\0';i++)
if(exp[i]>='a'&& exp[i]<='z'||exp[i]>='A'&& exp[i]<='Z')
{
temp=(tree*)malloc(sizeof(tree));
temp->ch=exp[i];
temp->next=NULL;
temp->prev=NULL;
push(temp);
}
else if(exp[i]=='+'||exp[i]=='-'||exp[i]=='*'||exp[i]=='/'||exp[i]=='^')
{
op1=pop();
op2=pop();
temp=(tree*)malloc(sizeof(tree));
temp->ch=exp[i];
temp->next=op1;
temp->prev=op2;
push(temp);
}
}
void display(tree *temp)
{
if(temp!=NULL)
{
display(temp->prev);
printf("%c",temp->ch);
display(temp->next);
}
}
main()
{
char exp[50];
printf("Enter the expression :");
scanf("%s",exp);
convert(exp);
printf("\n\n");
display(pop());
printf("\n\n");
getch();
}

Copy & Paste

#include<conio.h>
#include<stdio.h>
#include<stdlib.h>
int top=10;
struct tree
{
  char ch;
  struct tree *next;
  struct tree *prev;
}*stack[11];
typedef struct tree tree;

void push(tree *str)
{
  if(top<=0)
    printf("Stack is Full ");
  else
    {
      stack[top]=str;
      top--;
    }
}

tree* pop()
{
  tree *exp;
  if(top>=10)
    printf("Stack is Empty ");
  else
    exp=stack[++top];
  return exp;
}

void convert(char exp[])
{
  tree *op1,*op2;
  tree *temp;
  int i;
  for(i=0;exp[i]!='\0';i++)
    if(exp[i]>='a'&& exp[i]<='z'||exp[i]>='A'&& exp[i]<='Z')
      {
     temp=(tree*)malloc(sizeof(tree));
     temp->ch=exp[i];
     temp->next=NULL;
     temp->prev=NULL;
     push(temp);
      }
    else if(exp[i]=='+'||exp[i]=='-'||exp[i]=='*'||exp[i]=='/'||exp[i]=='^')
      {
     op1=pop();
     op2=pop();
     temp=(tree*)malloc(sizeof(tree));
     temp->ch=exp[i];
     temp->next=op1;
     temp->prev=op2;
     push(temp); 
      }
}

void display(tree *temp)
{
  if(temp!=NULL)
    {
      display(temp->prev);
      printf("%c",temp->ch);
      display(temp->next);
    }
}

main()
{
  char exp[50];
  printf("Enter the expression :");
  scanf("%s",exp);
  convert(exp);
  printf("\n\n");
  display(pop());
  printf("\n\n");
  getch();
}

Comments
bsit-ia barkada 2008-09-28 03:14:17
heller your code is not running.. but then thanks anyway...
bsit-ia barkada 2008-09-28 03:14:20
heller your code is not running.. but then thanks anyway...
Angel_Erikku 2009-03-05 08:20:27
....your code is not running...there are errors... hehe